1. Field
The present application generally relates to the design of a resist removal system and more particularly to a system and method for increasing strip rate and selectivity of resist strip over etch of silicon nitride or silicon dioxide using batch strip processing.
2. Related Art
Resist strip is a common process in semiconductor manufacturing and historically has been performed in a batch type processing mode with 25 to 100 substrates being immersed in a sulfuric acid and hydrogen peroxide mixture (SPM) for up to 20 minutes. As semiconductor devices shrink in size, a high defect rate is a significant challenge. To address the high defect rate associated with the batch strip processing, focus has switched to increasing the strip rate through a change of the variables of the treatment liquid used in the strip process. Furthermore, single substrate type processes are being developed and used where the cost of ownership and cost per substrate are justified.
For many reasons, economic and technical, single substrate SPM processes operate at higher temperatures (170-250 degrees C.) than batch processes (120-150 degrees C.). For example, to make single substrate SPM processing economically feasible, the resist strip time has to be reduced from about 10 minutes to ideally less than 2 minutes. This can be achieved with the higher process temperatures.
All-wet high dose ion implant resist strip (HDIRS) is also a driver for high temperature single substrate resist strip processing. A key advantage for single substrate processing is that higher temperatures can be utilized to strip the resist. Higher process temperatures have been shown to significantly improve resist strip performance for higher dosed resists (e.g. >1E′5 atoms/cm2). However, there are several disadvantages for using higher temperature in resist strip processing including: a) materials selected for use in the chamber materials must be stable in contact with treatment liquid at 225 degrees C., b) significant silicon nitride and silicon dioxide film loss is measured at temperatures above 170 degrees C., and c) a high level of mist can be generated in the process chamber. This is a challenge to make multi-chemical processing possible. For example, SPM processing is typically followed by a standard cleaning 1 (SC1) operation to remove residual particles from the substrate. Presence of SPM mist during the SC1 process creates a defect rate challenge evident in the following chemical reaction:H2SO4+NH4OH═NH4SO4+H2O  Reaction 1.0
Desirable in the art are methods and systems that can maintain a high strip rate for a resist and also maintain a high selectivity of strip over etch of silicon nitride or silicon dioxide. In addition, there is a need for a solution that enables high dose ion resist strip performance with lower treatment liquid process temperatures in contact with the substrate. A method and system in both batch and single substrate stripping systems must result in: a) materials compatibility concerns for use in the process chamber being reduced, b) less mist generation and associated improvement in multi-chemical process performance, and c) high resist strip performance with low silicon nitride and silicon dioxide loss. In summary, there is a need for batch strip treatment systems and methods and single substrate systems and methods that can achieve the goals of higher strip rate, higher strip selectivity, target strip time, and/or lower cost of ownership.